How to use the Compound Interest Calculator
- Enter your numbers – Starting amount, interest rate, compounding and time.
- Add deposits (optional) – A monthly or yearly amount, paid at the start or end of each period.
- Read the results – Final balance, interest earned, a chart and a year-by-year table.
About Compound Interest Calculator
Work out how much your savings or investment will be worth with compound interest. Enter the starting amount, the yearly interest rate, how often interest is compounded (yearly, half-yearly, quarterly, monthly, daily or continuously) and the time in years and months. Optionally add a regular monthly or yearly deposit at the start or end of each period. You get the final balance, how much you paid in, how much interest you earned, the effective annual rate, a year-by-year table, a growth chart and the formula A = P(1 + r/n)^(nt) filled in with your numbers. Everything is calculated in your browser.
Frequently asked questions
What is compound interest?
Interest that is added to your balance and then earns interest itself. 10,000 at 5% a year becomes 10,500 after one year and 11,025 after two – the extra 25 is interest on interest.
What is the compound interest formula?
A = P(1 + r/n)^(nt): P is the starting amount, r the yearly rate as a decimal (5% = 0.05), n how many times a year interest is added and t the number of years. With continuous compounding it is A = P·e^(rt).
Does compounding frequency matter much?
A little. 10,000 at 5% for 10 years gives 16,288.95 with yearly compounding, 16,470.09 monthly and 16,486.65 daily. The effective annual rate shows the difference: 5.000% vs 5.116% vs 5.127%.
What is the rule of 72?
A quick way to estimate how long it takes to double your money: divide 72 by the yearly rate. At 6% it takes about 72 ÷ 6 = 12 years (exactly 11.9 with yearly compounding).
Is the Compound Interest Calculator free?
Yes, completely free with no signup and no daily limit.
Does it work on my phone?
Yes. It works in any modern browser on iPhone, Android, Windows and Mac.
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